Conventionally, as means for supplying stabilized electric power with low thermal loss and in addition with comparatively high efficiency in cases where input-output differences are large, there have been widely used switching regulators (chopper regulators) that produce a desired output voltage from an input voltage by driving one end of an energy storage element (such as a capacitor or inductor) through the turning on and off of an output transistor (i.e., through the control of the on-duty thereof).
In conventional switching regulators, as shown in FIG. 3, an error amplifier ERR is provided for amplifying the difference between a feedback voltage Vfb varying according to the output voltage and a predetermined reference voltage Vref, and the output transistor N1 is driven according to an error voltage Verr produced by the error amplifier ERR.
In addition, in switching regulators required to respond quickly to load fluctuations, as shown in FIG. 3, the switch current Isw flowing through the output transistor N1 is detected, in the form of a sense voltage Vsense, with a sense resistor Rs, and the output transistor N1 is driven also according to the sense voltage Vsense (by so-called current mode control; for example, see patent document 1 below).
Patent document 1: JP-A-2000-92833.